1. Field of the Invention
This invention relates generally to systems and method for reading data from and writing data to data storage medium by employing the magnetic or optical recording technology. More particularly, this invention is related to a new servo data arrangement provided on data tracks on a planar medium surface for high accuracy positioning of a rotating head.
2. Description of the Prior Art
There are difficulties when conventional method and arrangement are employed for writing servo data on several data arcs for providing servo-control information to control the placement of pickup head on designated data arcs on a rotational-head data recording system. Unlike a conventional data recording and retrieving system, the pickup head of a rotational-head system is controlled to rotate over several data arcs. In contrast, in a conventional data recording and retrieving system, the pickup head is controlled to move over a linear direction transversal to the circular data tracks on the recording medium. For a rotational head data recording system, the relative motions between the pickup head and the data recording arcs are different from that of a conventional data recording system. Because of these differences in relative motions, the conventional methods of arranging servo-data sectors on each data track for recording the servo data are no longer useful. In the meantime, the pickup head must be controlled to accurately position over the designated locations on designated data arcs for performing the data recording and retrieving processes. For high density data recording system, precise placement is becoming even more important. It becomes critically important that the servo data recorded on servo-data sectors are employed to eliminate errors caused by dimensional variations, misalignment of mechanical parts, and other performance variations of electrical and optical components of the data recording system.
The rotational head data recording and retrieving system is disclosed in the invention is to resolve the difficulties of the conventional technology. In conventional data storage systems, the reading and writing of data are performed on concentric circular data tracks. The concentric data track configuration often presents a problem that the data-bit density varies between the outer tracks and the inner tracks. The variable bit density in data storage is due to a geometric factor that the outer data tracks are much longer in length that the inner tracks. A common practice is to form the inner tracks with a capacity to store the data bit at a higher bit density. A more complicate servo control system implemented with more complex signal-processing algorithms is required due to the variations of data storage density between different data tracks. Additionally, by varying the data storage density from the inner tracks toward the outside tracks, the data transfer rate is also changed in accessing data from the inner tracks then outside tracks. Such variation may also cause difficulties and complications in processing the data. Higher error rates may incur due to these variations between the inner tracks and the outer tracks.
Therefore, a need still exists for an improved data-card drive system with novel sector arrangement for writing servo-data in different data arcs to overcome the aforementioned difficulties encountered in the prior art. Specifically, the storage card drive system shall provide a uniform density for data storage and a data-card drive system with properly servo-sector arrangement to access the data-storage card. Furthermore, it would be desirable that this system is portable and is also provided with several standardized sizes for processing standardized data-storage cards.
Therefore, an object of the present invention is to provide a data storage-card drive system with a pickup head moving above the data-storage card in rotational movement. The data read-write functions are enabled only for arc-segments of the rotational movement guided by servo data written to servo sectors on the data arc with proper offsets. Also, the data tracks are arranged as plurality of parallel arcs, e.g., half-circles, and the servo data sectors are arranged to have offset between different arcs to overcome the aforementioned difficulties and limitations encountered in the prior art.
Specifically, it is an object of the present invention to provide a data-storage card drive system with a pickup head driven by a motor, e.g., a brushless motor, to rotate over the data-storage card with the rotation axis perpendicular to the card surface. The motor is mounted on a carriage for making horizontal movement along a longitudinal direction of the data card. The position of the pickup head is then servo-controlled with inter-arc offset arrangement of servo-data sectors for moving the carriage and the motor while the data storage card either stays at a fixed position or only pickup head is rotating and the card is making horizontal linear movements.
Another object of the present invention is to provide a data-storage card drive system for performing the data access tasks over a data storage medium surface, which has uniform data storage density. A new configuration of data-tracks formed as parallel arc or arc-segments, e.g., semi-circular data track, is implemented such that all data tracks have substantially the same length for data storage and the data bits are stored with uniform density.
Briefly, in a preferred embodiment, the present invention discloses a plurality of substantially parallel data arcs disposed on a flat data storage medium. The data arcs include at least two linearly aligned servo-data fields disposed in an inner data arc and an outer data arc with an inter-arc distance. The servo data field disposed on the outer data arc is disposed with an offset from an identical radial-angle position projected from a radial center to the servo data field of the inner data arc. The offset is substantially proportional to the inter-arc distance and substantially proportional to SIN (xcex8) where xcex8 is an angle between the identical radial-angle position and a linear-alignment direction between the two linearly aligned servo-data fields. Furthermore, the servo-data field on the outer data arc is disposed at a location with the offset from the identical radial-angle position in a direction toward a smaller radial angle projected from the radial center to the servo data field of the inner data arc.